An Assessment of Methods for the Estimation of Free Thyroxine

Three commercial kit methods for the estimation of free thyroxine (FT4) (Clinical Assays, Corning Medical, Damon Diagnostics) were evaluated. The effects of changes in thyroxine-binding globulin (TBG) and FT4 concentrations in these systems were assessed. Measurements were made in serum samples from...

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Bibliographic Details
Published inThe Journal of nuclear medicine (1978) Vol. 21; no. 6; pp. 529 - 539
Main Authors Witherspoon, Lynn R, Shuler, Stanton E, Garcia, Meredith M, Zollinger, Louise A
Format Journal Article
LanguageEnglish
Published United States Soc Nuclear Med 01.06.1980
Subjects
Evaluation Studies as Topic
Female
Humans
Hyperthyroidism - blood
Hypothyroidism - blood
In Vitro Techniques
Male
Radioimmunoassay - methods
Reagent Kits, Diagnostic
Thyroxine - blood
Thyroxine-Binding Proteins - analysis
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Summary:Three commercial kit methods for the estimation of free thyroxine (FT4) (Clinical Assays, Corning Medical, Damon Diagnostics) were evaluated. The effects of changes in thyroxine-binding globulin (TBG) and FT4 concentrations in these systems were assessed. Measurements were made in serum samples from hyperthyroid, hypothyroid, and euthyroid patients with different TBG concentrations, and results were correlated with functional thyroid status. The Clinical Assays and Damon Diagnostics assays were found to be essentially independent of binding-protein concentration effects and responded appropriately to changes in FT4 concentration. The method of Corning Medical does not measure FT4 directly but yields an FT4 index calculated from a TBG-dependent T4 uptake and the total T4 concentration. This corning index yields falsely elevated results in patients with marked elevation in TBG concentration.
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ISSN:0161-5505
1535-5667